Device and method for aseptic pressure relief

ABSTRACT

The invention relates to an overpressure safety device ( 1 ) for pipeline networks, comprising an inlet pipe leading from the pipeline network to be secured to the overpressure safety device ( 1 ), at least one safety valve, and a discharge pipe. According to the invention, at least two safety valves ( 2, 3 ) are provided, and both safety valves comprise an inlet side and an outlet side, wherein the first safety valve ( 2 ) is connected to a pipe of the pipeline network, and the first is connected to the second safety valve ( 3 ) by a connecting pipeline ( 4 ). The connecting pipe ( 4 ) thereby has an inlet pipe and a discharge pipe, by means of which a liquid or gaseous purge, cleaning, and/or sterilization agent can be fed in and discharged.

The invention relates to pressure relief device (1) for pipeline networks, said pressure relief device comprising a supply line, which leads from the pipeline network to be made safe to the pressure relief device (1), and has at least one safety valve and one discharge line. The most important feature in this case is that at least two safety valves (2) (3) are provided, and the two safety valves have an inlet side and an outlet side, wherein the first safety valve (2) is connected to a line of the pipeline network, and the first is connected to the second safety valve (3) via a connecting pipeline (4). In this case the connecting pipeline (4) has a supply line and a discharge line, by means of which a liquid or gaseous flushing, cleaning and/or sterilizing agent can be supplied or removed.

In filling operations for sterile products, in particular when demanding licenses are aspired to, such as for example FDA licenses, conventional safety valves are not sufficient. Conventional safety valves, as a rule, have a spring-loaded valve body, which automatically opens at a certain limit pressure. These types of safety valves are known and have been described many times in patent literature. For example, EP 0 022 941 A1, EP 0 051 082 A1, DE 37 42 722 A1 and DE 196 07 840 C1, to name but a few.

In pipeline systems that are to be kept sterile, in the event of surges there is the risk that the valve may open briefly to the non-sterile blow-off line and recontamination may occur. When said conventional safety valves are used in filling processes for foodstuffs, in particular in the case of beverages, the risk of recontamination is reduced by the housing of the safety valve being continuously traversed by steam, albeit in a pressureless manner. This method of operation results in the pipeline network being permanently heated locally, which, through heat conduction inside the metal pipeline materials, leads to a simple temperature increase in more remote regions, with no sterilizing effect. Such a slight temperature increase, in its turn, accelerates microbial growth. In addition, there are energy problems linked with this solution.

The use of a rupture disc is known and said rupture disc is coupled to a safety valve that is connected downstream. The rupture disc closes off in a more or less flush manner with the pipeline and is treated on one side by means of the usual cleaning and sterilizing routines. This solution makes it possible, in the event of the rupture disk breaking, for the process to be able to be terminated in a controlled manner. A disadvantage of the use of rupture discs is the costs involved when a rupture disc is lost and the subsequent time and money spent on labour and cleaning when a rupture disc has to be replaced. Consequently, it is the object of the invention to disclose a device that eliminates the abovementioned disadvantages.

This is achieved through a pressure relief device (1) for pipeline networks, said pressure relief device comprising a supply line, which leads from the pipeline network to be made safe to the pressure relief device (1) and has at least one safety valve and one discharge line. The most important feature in this case is that at least two safety valves (2) (3) are provided, and the two safety valves have an inlet side and an outlet side, wherein the first safety valve (2) is connected to a line of the pipeline network, and the first is connected to the second safety valve (3) via a connecting pipeline (4). In this case the connecting pipeline (4) has a supply line and a discharge line, by means of which a liquid or gaseous flushing, cleaning and/or sterilizing agent can be supplied or removed.

In an ideal manner, the first safety valve (2) is designed or adjusted in such a manner that said safety valve withstands a higher limit pressure than the safely valve (3). This design makes it possible for the opening of the first safety valve not to result in non-sterility, but rather for the method not to have to be interrupted subsequent to a pressure blow or a pressure peak. The pipe interior of the connecting pipeline can be acted upon after such an event and routinely with a suitable sterilizing agent, such as for example steam, active oxygen, H₂O₂ or peracetic acid. Limit pressure refers in this case to the level of pressure at which the respective safety valve opens.

In an advantageous manner, the load capacity of the safety valves is such that the limit pressure of the second safety valve (3) is 50% less than the limit pressure of the first safety valve (2) or even less. In this case care must be taken to ensure that the pressure of the sterilizing medium that is conducted through the connecting pipeline is below the limit pressure of the second safety valve.

Flow management in the connecting pipeline (4) can be problematic in particular when liquid sterilizing media are used, such that in the case of an improved variant the supply line of the sterilizing medium leads directly into outlet side of the first safety valve (2) and the discharge line is connected directly to the inlet side of the second safety valve (3). This ensures that a defined flow is effected in the connecting pipeline (4).

It is possible to improve this variant even more by the end of the supply line in the outlet side or in the connecting pipeline being oriented in such a manner that its outlet is directed onto the valve seat of the first safety valve (2). Consequently, highly effective sterilization of the valve seat is ensured as fast as possible. For this reason, the end of the supply line should be a maximum of 20 mm away from the valve seat of the first safety valve (2).

A further improvement is that a plurality of supply lines lead into the connecting pipeline (4) or that at least one outlet of the supply line is directed onto the two valve seats, the valve seat of the first and of the second safety valve.

In an advantageous manner, a condensate separator is located in the discharge line and the connecting pipeline (4) is located or shaped in such a manner that condensate can drain away freely.

The invention also comprises a method for pressure relief in pipeline networks, said method including an embodiment of the aforementioned devices.

The invention is shown by way of two exemplary embodiments in FIGS. 1 and 2.

FIG. 1 shows a schematic representation of the basic arrangement

FIG. 2 shows a special arrangement of the outlets inside the connecting pipeline.

FIG. 1 shows a schematic representation of the pressure relief device 1, comprising the two safety valves 2 and 3. The first safety valve 2, with a limit pressure of 5.5 bars, and the second safety valve 3, with a limit pressure of 2.0 bars, are connected by means of the connecting pipeline 4. The safety valve 2 is connected by means of a pipe connection 5 to the pipeline 6, which is part of the pipeline network to be monitored (not represented). A supply line 7 leads to the connecting pipeline 4, a controlled valve 8 and a non-return-valve 9 being located in the line path of said supply line. The arrow indicates the direction of flow of the sterilizing medium.

The discharge line 10, which is connected to the condensate separator 11, leads away from the connecting pipeline 4. The pressure relief device 1 shown in FIG. 1 is ideally acted upon with steam. The steam forms an active sterile block. If necessary, it is possible to sterilize the intermediate space in a continuous manner. The particular advantage is that even if the bellows is faulty, no contamination can move into the pipeline system by means of the valve shaft.

If there are product leakages in the first safety valve 2 in the event of pressure peaks in the pipe 6, these drain away together with the condensate. In the case of cleaning, the two safety valves are clocked together. In the case of sterilizing, the valves do not need to be clocked because the hot water in the product pipeline together with the steam in the connecting pipeline 4 heats up and sterilizes the valve seat in a sufficient manner. An outflow 20 is provided below the outlet side 19 of the second safety valve 3.

FIG. 2 also shows a schematic representation of the pressure relief device, which is suitable in particular for the use of a liquid sterilizing medium. The supply line 7 branches off in the connecting pipeline into a left-hand and a right-hand branch. The right-hand branch leads into the outlet side 12 of the first safety valve 2 and the outlet 13 of the right-hand branch of the supply line 7 is directed directly onto the valve seat 14.

The left-hand branch of the supply line 7 leads into the inlet side 15 of the second safety valve 3 and the outlet 16 directly faces the valve seat 17 and is directed onto said valve seat. A widening is provided in the region of the flange 18 so that residual liquid or condensate can collect there and drain away. The discharge line 10 is also located in this region. This arrangement ensures ideal flow management in the connecting pipeline 4. 

1. A pressure relief device for pipeline networks, said pressure relief device comprising: a supply line, which leads from a pipeline network to be made safe to the pressure relief device, and in addition has at least one safety valve and one discharge line, at least two safety valves, the at least two safety valves including a first safety valve having an inlet side and an outlet side, the first safety valve being connected to a line of the pipeline network; and a second safety valve having an inlet side and an outlet side, the second safety valve being connected to the first safety valve via a connecting pipeline, wherein the connecting pipeline has a supply line and a discharge line, by means of which a liquid or gaseous flushing, cleaning and/or sterilizing agent can be supplied or removed.
 2. The pressure relief valve of claim 1, wherein the first safety valve is configured to withstand a higher limit pressure than the second safety valve.
 3. The pressure relieve valve of claim 2, wherein the first and second safety valves each have a limit pressure, and wherein the limit pressure of the second safety valve is 50% or less than the limit pressure of the first safety valve.
 4. The pressure relief valve of claim 1, wherein the supply line leads into the outlet side of the first safety valve and the discharge line leads into the inlet side of the second safety valve.
 5. The pressure relief valve of claim 1, wherein the end of the supply line in the outlet side or in the connecting pipeline is oriented in such a manner that its outlet is directed onto a valve seat of the first safety valve.
 6. The pressure relief valve of claim 5, wherein the end of the supply line is a maximum of 20 mm away from the valve seat of the first safety valve.
 7. The pressure relief valve of claim 1, further comprising a plurality of supply lines that lead into the connecting pipeline.
 8. The pressure relief valve of claim 1, wherein at least one outlet of the supply line is directed onto a valve seat of the first safety valve and a valve seat of the second safety valve.
 9. The pressure relief valve of claim 1, further comprising a condensate separator located in the discharge line, and wherein the connecting pipeline is located or shaped to drain condensate.
 10. A method for pressure relief in pipeline networks, said method comprising: providing a pressure relief device comprising a supply line, which leads from the pipeline network to be made safe to the pressure relief device, the supply line having at least one safety valve and one discharge line, at least two safety valves, the at least two safety valves including a first safety valve having an inlet side and an outlet side, the first safety valve being connected to a line of the pipeline network; a second safety valve having an inlet side and an outlet side, the second safety valve being connected to the first safety valve via a connecting pipeline, wherein the connecting pipeline has a supply line and a discharge line, by means of which a liquid or gaseous flushing, cleaning and/or sterilizing agent can be supplied or removed.
 11. The method of claim 10, further comprising selecting a sterilizing agent from a group consisting of steam, active oxygen and a mixture of steam and active oxygen.
 12. The method of claim 10, further comprising selecting a sterilizing agent from a group consisting of H₂O₂ and peracetic acid. 